A computer-controlled 100-channel High-Speed Diode Array Spectrophotometer has been developed by the Biomedical Engineering and Instrumentation Program of the National Center for Research Resources and DSB for the Laboratory of Cell Biology (LCB), NHLBI. It will be used to obtain more complete spectral information about the rapid changes of the reduction and oxidation centers within the protein enzyme cytochrome oxidase. This enzyme is involved in cellular respiration and is located within the inner lipid bilayer of the mitochondrion. The electronic hardware consists of two 48-element photodiode arrays, each connected to a discrete A/D converter and, subsequently, to local storage channels. Each channel is capable of acquiring data every 10 microseconds. A fast personal computer (PC) is used to control the spectrophotometer. Timing control signals are transmitted from the PC, and the PC receives data from the A/D channels via a 40-bit parallel interface. DSB assisted in developing the PC interface to the spectrophotometer and in creating the data acquisition and control software. The commercial modeling system MLAB is being used for analysis of the data. The spectrophotometer has been built and delivered to NHLBI. Laboratory testing of both the hardware and the software systems has been completed. This instrument will open up a variety of new applications. The increased temporal resolution will permit investigation of early events in biochemical reaction kinetics that have been impossible to measure before. Additional computer-controlled timing for up to five experiment functions such as laser, stop-flow, and start A/D have been added this year. A high-resolution computer-controlled stop-flow device will be added to the system. An invention report has been filed by BEIP.